• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.925-928
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• 2014

A dye-sensitized solar cell (DSSC) was fabricated with a nanocrystalline $TiO_2$ film electrode on FTO glass, N719 dye, electrolytes (or $CsSnI_3$), and counter Pt electrode by incorporating it with single-walled carbon nanotubes (SWNTs). SWNTs were combined with $TiO_2$ film, $CsSnI_3$, Pt electrode, separately, and the SWNT-containing cell was compared with a pristine cell in cell performance. We also examined the performance change by pressing $TiO_2$ film, during cell fabrication, inside a high pressure chamber. Mostly, the change of conversion efficiency was compared for each cell, and an atomic force microscopy data were suggested to explain our results.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.75-75
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• 2011

Recently, dye-sensitized solar cell (DSSC) attracts great attention as a promising alternative to conventional silicon solar cells. One of the key components for the DSSC would be the nanocrystalline TiO2 electrode, and the control of interface between TiO2 and TCO is a highly important issue in improving the photovoltaic conversion efficiency. In this work, we applied various interfacial layers, and analyzed their effect in enhancing photovoltaic properties. In overall, introduction of interfacial layers increased both the Voc and Jsc, since the back-reaction of electrons from TCO to electrolyte could be blocked. First, several metal oxides with different band gaps and positions were employed as interfacial layer. SnO2, TiO2, and ZrO2 nanoparticles in the size of 3-5 nm have been synthesized. Among them, the interfacial layer of SnO2, which has lower flat-band potential than that of TiO2, exhibited the best performance in increasing the photovoltaic efficiency of DSSC. Second, long-range ordered cubic mesoporous TiO2 films, prepared by using triblock copolymer-templated sol-gel method via evaporation-induced self-assembly (EISA) process, were utilized as an interfacial layer. Mesoporous TiO2 films seem to be one of the best interfacial layers, due to their additional effect, improving the adhesion to TCO and showing an anti-reflective effect. Third, we handled the issues related to the optimum thickness of interfacial layers. It was also found that in fabricating DSSC at low temperature, the role of interfacial layer turned out to be a lot more important. The self-assembled interfacial layer fabricated at room temperature leads to the efficient transport of photo-injected electrons from TiO2 to TCO, as well as blocking the back-reaction from TCO to I3-. As a result, fill factor (FF) was remarkably increased, as well as increase in Voc and Jsc.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.2
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• pp.354-356
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• 2017

We focused on light management technology in amorphous silicon solar cells to suppress increase in absorber thickness for improving power conversion efficiency (PCE). $MgF_2$ and $TiO_2$ anti-reflection layers were coated on both sides of Asahi VU ($glass/SnO_2:F$) substrates, which contributed to increase in PCE from 9.16% to 9.81% at absorber thickness of only 150 nm. Also, we applied very thin $MgF_2$ as a rear reflector at n-type nanocrystalline silicon oxide/Ag interface to boost photocurrent. By reinforcing rear reflection, we could find the PCE increase from 10.08% up to 10.34% based on thin absorber about 200 nm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.4
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• pp.754-758
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• 2010

In general, Dye-sensitized Solar Cells(DSCs) consist of the nanocrystalline titanium dioxide($TiO_2$) layer which is fabricated on a transparent conductive oxide(TCO) layer such as $F/SnO_2$ glass, a dye adhered to the $TiO_2$, an electrolyte solution and platinum-coated TCO. Among these components, two TCO substrates are estimated to be about 60% of the total cost of the DSCs. Currently novel TCO-less structures have been investigated in order to reduce the cost. In this study, TCO-less DSCs consisting of titanium electrodes were investigated. The titanium electrode is deposited on top of the porous $TiO_2$ layer using electron-beam evaporation process. The porosity of the titanium electrode was found out by the SEM analysis and dye adhesion. As a result, when the thickness of the titanium electrode increased, the surface resistance decreased and the conversion efficiency increased relatively.

• Journal of Powder Materials
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• v.15 no.6
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• pp.450-457
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• 2008

The objectives of this study were the development of a synthesis technique for highly active nanosized ITO powder and the understanding of the reaction mechanisms of the ITO precursors. The precipitation and agglomeration phenomena in ITO and $In_{2}O_{3}$ precursors are very sensitive to reaction temperature, pH, and coexisting ion species. Excessive $Cl^-$ ion and $Sn^{+4}$ ions had a negative effect an synthesizing highly active powders. However, with a relevant stabilizing treatment the shape and size of ITO and $In_{2}O_{3}$ precursors could be controlled and high density sintered products of ITO were obtained. By applying the reprecipitation process (or stabilization technique), highly active ITO and $In_{2}O_{3}$ powders were synthesized. Sintering these powders at $1500^{\circ}C$ for 5 hours produced 97% dense ITO bodies.

• Bulletin of the Korean Chemical Society
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• v.30 no.10
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• pp.2329-2337
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• 2009

Three heteroleptic ruthenium sensitizers, Ru(L)($L^1)(NCS)_2$ [L = 4,4'-dicarboxylic acid-2,2'-bipyridine, Ru-T1: $L^1$ = (E)-2-(4'-methyl-2,2'-bipyridin-4-yl)-3-(thiophen-2-yl)acrylonitrile, Ru-T2: $L^2$ = (E)-3-(5'-hexyl-2,2'-bithiophen-5- yl)-2-(4'-methyl-2,2'-bipyridin-4-yl)acrylonitrile, and Ru-T3: $L^3$ = (E)-3-(5"-hexyl-2,2':5',2"-terthiophen-5-yl)-2- (4'-methyl-2,2'-bipyridin-4-yl)acrylonitrile)], were synthesized and used as photosensitizers in nanocrystalline dyesensitized solar cells (DSSCs). The introduction of the 3-(5-hexyloligothiophen-5-yl)acrylonitrile group increased the conjugation length of the bipyridine donor ligand and thus improved their molar absorption coefficient and light harvesting efficiency. DSSCs with the configuration of Sn$O_2$: F/Ti$O_2$/ruthenium dye/liquid electrolyte/Pt devices were fabricated using these Ru-$T1{\sim}T3$ as a photosensitizers. Among the devices, the DSSCs composed of Ru-T2 exhibited highest power conversion efficiency (PCE) of 2.84% under AM 1.5 G illumination (100 mW/$cm^2$).

• Journal of Powder Materials
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• v.9 no.6
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• pp.394-408
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• 2002

Nanostructured high strength metastable Al-, Mg- and Ti-based alloys containing different amorphous, quasicrystalline and nanocrystalline phases are synthesized by non-equilibrium processing techniques. Such alloys can be prepared by quenching from the melt or by powder metallurgy techniques. This paper focuses on one hand on mechanically alloyed and ball milled powders containing different volume fractions of amorphous or nano-(quasi)crystalline phases, consolidated bulk specimens and, on the other hand. on cast specimens containing different constituent phases with different length-scale. As one example. $Mg_{55}Y_{15}Cu_{30}$- based metallic glass matrix composites are produced by mechanical alloying of elemental powder mixtures containing up to 30 vol.% $Y_2O_3$ particles. The comparison with the particle-free metallic glass reveals that the nanosized second phase oxide particles do not significantly affect the glass-forming ability upon mechanical alloying despite some limited particle dissolution. A supercooled liquid region with an extension of about 50 K can be maintained in the presence of the oxides. The distinct viscosity decrease in the supercooled liquid regime allows to consolidate the powders into bulk samples by uniaxial hot pressing. The $Y_2O_3$ additions increase the mechanical strength of the composites compared to the $Mg_{55}Y_{15}Cu_{30}$ metallic glass. The second example deals with Al-Mn-Ce and Al-Cu-Fe composites with quasicrystalline particles as reinforcements, which are prepared by quenching from the melt and by powder metallurgy. $Al_{98-x}Mn_xCe_2$ (x =5,6,7) melt-spun ribbons containing a major quasicrystalline phase coexisting with an Al-matrix on a nanometer scale are pulverized by ball milling. The powders are consolidated by hot extrusion. Grain growth during consolidation causes the formation of a micrometer-scale microstructure. Mechanical alloying of $Al_{63}Cu_{25}Fe_{12}$ leads to single-phase quasicrystalline powders. which are blended with different volume fractions of pure Al-powder and hot extruded forming $Al_{100-x}$$(Al_{0.63}Cu_{0.25}Fe_{0.12})_x$ (x = 40,50,60,80) micrometer-scale composites. Compression test data reveal a high yield strength of ${\sigma}_y{\geq}$700 MPa and a ductility of ${\varepsilon}_{pl}{\geq}$5% for than the Al-Mn-Ce bulk samples. The strength level of the Al-Cu-Fe alloys is ${\sigma}_y{\leq}$550 MPa significantly lower. By the addition of different amounts of aluminum, the mechanical properties can be tuned to a wide range. Finally, a bulk metallic glass-forming Ti-Cu-Ni-Sn alloy with in situ formed composite microstructure prepared by both centrifugal and injection casting presents more than 6% plastic strain under compressive stress at room temperature. The in situ formed composite contains dendritic hcp Ti solid solution precipitates and a few $Ti_3Sn,\;{\beta}$-(Cu, Sn) grains dispersed in a glassy matrix. The composite micro- structure can avoid the development of the highly localized shear bands typical for the room temperature defor-mation of monolithic glasses. Instead, widely developed shear bands with evident protuberance are observed. resulting in significant yielding and homogeneous plastic deformation over the entire sample.